Upon normal physiological conditions, hemostasis, the readiness of the blood to clot to prevent blood loss, is kept in hemostatic balance by feedback mechanisms. The hemostatic balance is dependent on both the pro and anticoagulant pathway as well as the fibrinolytic system. In case the hemostatic balance is out of equilibrium, pathological clotting (vessel blockage) or bleeding (hemorrhage) can supplant normal hemostasis.
Abnormalities of the hemostatic system can be acquired or congenital. In such cases it is clinically essential to diagnose, monitor, and manage the patient in order to optimize therapeutic intervention.
Most coagulation testing involves end-point assays, which detect the clotting time of blood plasma or the real time clot lysis by means of turbidimetry. Although performed routinely, the currently available coagulation assays have inherent limitations that make them potentially unreliable as tools for monitoring increased coagulation. Moreover, there is not always a good correlation between the results of coagulation tests and the prevention of postoperative haemorrhage or recurrent thrombosis.
Most of the limitations relate to the fact that these are end-point tests that measure the time of clot formation in vitro and require the addition of exogenous reagents (such as Ca2+ ions to replenish those bound by an anticoagulant), and thus do not necessarily reflect the patient's thrombotic potential (clotting potential).
As compared to the tests described above EP-420 332 discloses an improved thrombin generation assay. In this assay not only information is gathered about the clotting of plasma but also about the total thrombin generation after clot formation. These assays were first performed with chromogenic substrates and later on with fluorogenic substrates. Furthermore, several thrombin generation assays with platelet poor and platelet rich plasma are disclosed.
In these assays again the limitation is the measurement of increased coagulability (thrombophilia). Thrombophilia is a term used to describe a group of conditions in which there is an increased tendency, often repeated and often over an extended period of time, for excessive clotting.
A need therefore exists for a new assay that does not have the above indicated drawbacks, that is more simple and can measure the fibrinolysis in dependency of thrombin generation. It is the object of the invention to provide such assay.